The present invention relates to selected 2-aryl-2H-benzotriazoles which are useful in protecting light-sensitive organic materials from deterioration and to stabilized compositions containing said benzotriazoles.
The UV-absorber of the o-hydroxyphenyl-2H-benzotriazole class have long been known as effective light stabilizers for organic materials and have enjoyed considerable commercial success.
The description, preparation and uses of these valuable 2-aryl-2H-benzotriazoles are further taught in U.S. Pat. Nos. 3,004,896; 3,055,896, 3,072,585; 3,074,910; 3,189,615 and 3,230,194.
However the hitherto known as 2-aryl-2H-benzotriazoles of this group have in some circumstances exhibited limited compatibility in certain substrates, and excessive tendency to exude, sublime and/or volatilize during processing of stabilized compositions into sheets, films, fibers or other pellicles when processing must be done at elevated temperatures. Likewise such benzotriazoles may also suffer undue loss by volatilization or sublimation from fabricated structures, particularly thin films or coatings, especially when subjected to elevated temperatures during use.
Attempts have been made to increase compatibility and to reduce volatilization loss by modifying the structure of the benzotriazoles.
In U.S. Pat. No. 3,230,194, a higher alkyl group was substituted for methyl and the latter compound 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole exhibited superior compatibility and performance in polyethylene compound to former.
Still other attempts were made to increase the compatibility of the aryl-2H-benzotriazole molecules in polymeric substrates and to decrease the tendency of said molecules to volatilize during processing and/or use by substituting the phenolic ring of said compounds with aralkyl groups such as benzyl, .alpha.-methylbenzyl and .alpha.,.alpha.-dimethylbenzyl radicals. Such compounds are disclosed in U.S. Pat. No. 4,127,586; Japanese Kokai No. 158588/75 and copending U.S. patent application Ser. No. 918,984.
Surprisingly, the instant compounds such as 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole having only alkyl substitution on the phenolic ring of the benzotriazole exhibit an excellent combination of compatibility with and/or solubility in numerous polymeric substrates along with superior resistance to loss from stabilized compositions during high temperature processing or in end use applications where coatings or films of the stabilized compositions are exposed even to ambient weathering and light exposures compared to stabilized compositions containing the closest 2-aryl-2H-benzotriazoles of the prior art.
In U.S. Pat. No. 4,041,044, an improved process for making 2-aryl-2H-benzotriazoles is taught. In said specification, a number of phenols and some twelve preferred phenols useful in said process are listed, inter alia 2,4-di-tert-octylphenol. Neither instant compound 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole nor 5-chloro-2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole was exemplified nor prepared in said reference and the outstanding properties of these compounds now seen compared to other prior art benzotriazoles were not then recognized from among the myriad of possible compounds disclosed in this reference.
A dyeable stabilized polymer blend comprising polypropylene, a polyetherester, two phenolic antioxidants, a thiosynergist and 2-(2-hydroxy-3,5-dioctylphenyl)-2,1,3-benzotriazole is disclosed in U.S. Pat. No. 3,487,453. The exact chemical structure of the "dioctyl" substitution on the aryl-2H-benzotriazole moiety is not further identified nor can what influence or effect the benzotriazole exerted in this complex mixture of stabilizers in polypropylene be discerned.